Bacterial pathogens present a threat to the health and safety of patients wherever an area of skin is penetrated. For example, such pathogens may be a hazard during surgical procedures. Without adequate disinfection of the incision site prior to surgery, surface microorganisms or "skin flora" may transfer into the incision during surgery, resulting in internal infections after closure of the incision. To prevent such infections, known as "septic infections," it is critical to disinfect the incision site prior to surgery with a disinfectant that possesses a high antimicrobial activity and a broad spectrum of action. Since surgical procedures can last for many hours, it is also important that the initial disinfection of the incision site provide antimicrobial activity for an extended period of time.
In the United States, the Food and Drug Administration requires that a presurgical skin disinfectant be capable of reducing the number of flora on dry skin areas, such as an abdomen, by at least 2.5 logs or to levels that are too low for reliable quantification (less than about 25 cfu/cm.sub.2). On moist skin, such as inguinal areas, the disinfectant must reduce the initial bacterial population by a minimum of 3.2 logs (1.5.times.10.sup.3 cfu/ml), and maintain this level of bacteriostasis for at least four hours.
Presently, two antimicrobial materials have the requisite antimicrobial activity and longevity for use as a presurgical disinfectant. Both chlorhexidine gluconate (sold, for example, under the trademark HIBICLENS) and iodophors (sold, for example, under the trademark BETADINE) can protect patients from septic infections. However, these products require double applications and extended scrubbing with intervening wiping in order to adequately reduce microbial counts. For example, HIBICLENS calls for two individual 2- to 3- minute skin scrubbings, each with fresh material, with the final scrub allowed to dry on the skin. Similarly, BETADINE requires two 4-minute scrubbings, with the final scrub also allowed to dry on the skin. This lengthy scrubbing and drying period increases the time required to prepare a patient for surgery. The use of these products is therefore very costly, tying up the operating theater and a staff of medical professionals for the duration of the disinfecting process.
A disinfecting system that can function more rapidly, and thus reduce skin disinfection times significantly, is the chlorous acid system as described in U.S. Pat. No. 4,986,990. In that system, chlorous acid is produced in an aqueous medium by mixing a metal chlorite with a protic acid. The chlorous acid then degrades to a series of cidal oxidants, including chlorine dioxide, which collectively form the active disinfecting system.
Chlorous acid compositions can retain their antimicrobial activity for an extended period of time in dilute aqueous solution. However, these compositions lose their disinfecting properties when the aqueous solvent evaporates. Upon evaporation of the solvent, the chlorite ion converts to the corresponding chlorous acid form (HClO.sub.2) and then to solid, inert residues of chloride and chlorate salts as the gaseous ClO.sub.2 evaporates. As a result, these compositions have an active life of only a few minutes if used for presurgical skin disinfection.
Film-forming polymers can be used to generate intact films that remain on the skin for many hours after application, and such films may provide a physical barrier against deposition of environmental microorganisms on the skin at surgical sites. However, the use of film-forming polymers has not resulted in prolonging antimicrobial activity to supplement the protection afforded by the physical barrier of the film. In addition, there are only a few gelling agents that are stable in both the chlorite component solution and the acidic chlorous acid disinfecting composition. To date, only a polysulfonic acid polymer has been used in conjunction with the chlorous acid system disclosed in U.S. Pat. No. 4,891,216. The resulting composition, however, was found to generate a final film that was too tacky to be aesthetically acceptable. Thus, in spite of the potential advantages associated with the use of the chlorous acid system for presurgical disinfection, the extended 4-hour bacteriostasis required by the FDA has yet to be been attained for this system.
Extended disinfection is similarly important for non-surgical skin openings. For example, in disinfecting wound sites, it is important in many situations to not only destroy all contaminating pathogenic organisms, but to protect the wounds from subsequent contamination by environmental pathogen carriers such as air and clothing. Bandaging of sites will offer some protection as a physical barrier to environmental contamination, but often bandaging materials are counterindicated (e.g., on burned skin areas). No currently available skin antiseptic can provide the needed long-term disinfection (e.g., disinfection for a clay or more).
The areas surrounding in-dwelling catheters represent additional sites where both initial antisepsis and continued protection from bacterial penetration, over many days, is a necessity. Initial disinfection with, for example, alcohol, iodophors or chlorhexidine prior to insertion of a catheter is usually effective, but the region around the insertion site and the incised tissue is susceptible to rapid growth of contaminating pathogens.
In a like manner, blood-drawing sites (i.e., in the elbow crease) can represent surface areas where bacterial invasion may occur. This is increasingly likely for frequent blood donors, or for those individuals from whom blood samples are often taken. Frequent transdermal penetration in these areas results in tissue scarring (overtly visible and otherwise), characterized by uneven skin surfaces harboring organisms which are difficult to reach and destroy. When such areas are subsequently penetrated during injections or for blood transfusion, small sections of contaminated tissue can be carried directly into the blood stream. In such cases the prior application to these surfaces of a topical antiseptic with protracted antimicrobial activity would help in destroying these poorly accessible organisms.
Accordingly, there is a need in the art for a presurgical skin disinfectant of high antimicrobial capacity that can be applied rapidly in a single application, and that retains its disinfecting properties over the extended time periods of some surgical procedures. There is a similar need in the art for a topical antiseptic for use on wounds and injection or insertion sites that maintains a high antimicrobial activity for extended periods. The present invention fulfills these needs, and provides further related advantages.